Angled-disc valves are known in the art--see for example U.S. Pat. Nos. 3,126,193 and 3,779,511. In general, such valves comprise a rotatable valve stem disposed at a 45.degree. angle to a straight passage and a disc disposed at a 45.degree. angle to the valve stem, rotation of the stem about its longitudinal axis thus causing the disc to move between perpendicular closed and parallel open positions with respect to the passage. Such valves are highly desirable because they are relatively simple but quite effective, and they are particularly desirable for sanitary applications since they do not tend to trap material in a manner that precludes effective conventional cleaning. Heretofore, however, such valves have used single discs and it has not been apparent that they could be used for applications such as diverter valves.
Diverter valves having two discs on a common stem are also known--see for example U.S. Pat. Nos. 1,313,762 and 1,482,413. Prior constructions of this type are not entirely suitable, however, since they require that the main and branch passages be essentially parallel as opposed to the perpendicular orientation generally desired for ease of manufacture and use in connection with standard components, and because there are at least two shaft entry or exit openings which makes cleaning more difficult. Other diverter valves have perpendicular passages, but use complicated linkages or other arrangements that are expensive, may be difficult to maintain, and may tend to trap materials.